Widely used in optic-fiber communications and interconnections, vertical-cavity surface-emitting lasers (VCSEL) are sensitive to optical feedback and optical injection. These perturbations can induce rich nonlinear dynamical behaviors, such as spectral broadening, irregular and chaotic pulsations, and polarization instabilities. Since VCSELs often operate with several transverse modes when the bias current goes up, complexity of the system increases due to spatial profiles of different transverse modes. Therefore dynamics induced by optical injection and feedback is a topic of significant research interests for both fundamental science and engineering applications. In particular, both optical feedback and optical injection play key roles in chaos synchronization of two lasers, which is of interest to secure data communications. Chaos synchronization is also a fundamental property of coupled, time-delay systems. We investigate experimentally perturbation-induced polarization and transverse dynamics of VCSELs. In the multi-transverse mode regime, we study dynamical routes to chaotic regime, interplay of optical feedback and current modulation, and effects of optical injection of two frequencies. The obtained results help us to achieve chaos synchronization of two multimode VCSELs and to validate corresponding theoretical results.
As described above, a VCSEL is an ideal vehicle for studying dynamic in complex systems and a promising device in fiber-optic communications. Our study on nonlinear dynamics of multi-transverse-mode VCSELs subject to perturbations will produce interesting results for scientists who study nonlinear dynamics and laser physics. The results will also be useful to community of optic-fiber communications because multimode VCSELs have been used in local area network (LAN) due to their lower modal noise and because chaos synchronization is important for secure data transmission. The project enhances undergraduate education by integrating research with undergraduate training and learning. Students are involved in the project through summer research, senior theses, and independent studies. Besides, experiments and demonstrations that utilize VCSELs are introduced in advanced courses and laboratory. Local high school students and teachers can benefit from the project through joining the research and visiting the PI's laboratory.
